Control method and apparatus



Jan. 26, 1954 R. J. coAR CONTROL METHOD AND APPARATUS 6 Sheets-Sheet l Filed May 21, 1947 INVENTOR filial Jan. 26, 1954 R. J. coAR CONTROL METHOD AND APPARATUS Filed May 21,'1947 6 Sheets-Sheet 2 lll/Il giggl- INVENTOR Rz'ceazwl .l oa? ATTORNEY Jan. 26, 1954 R. J. coAR 2,667,150

CONTROL METHOD AND APPARATUS Filed May 21, 1947 e sheets-sheet '5 R. J. COAR CONTROL METHOD AND APPARATUS Jan. 26, 1954 6 Sheets-Sheet 4 Filed May 21, 194? jan. 26, 1954 R 1, @OAR 2,667,150

CONTROL METHOD AND APPARATUS Filed May 2l, 1947 6 SheetS-Sheet 5 Jan. 26, 1954 R. J. coAR CONTROL METHOD AND APPARATUS 6 Sheets-Sheet 6 Filed May 21, 1947 Patented Jan. 26, 1954 Ulrso srA'rEs e OFFICE CONTROL METHOD AND APPARATUS Application May 21, 1947, Serial N0. 749,430

(Cl. 12S-119) 24 Claims.

This invention relates to a control method and apparatus, particularly for hydraulically driven variable speed aircraft engine supercharging blowers.

A principal object of the invention is to provide an improved system for the manifold pressure regulation of a supercharged engine.

Another object of the invention is to .provide a stable system for regulating the manifold pressure of an aircraft engine in which the pilot obtains improved feel, i. e. a system in which any change in the pilots selection of manifold pressure is followed quickly by a corresponding change in manifold pressure.

Another object is to provide means for regulating the outlet pressure of a hydraulically driven variable speed blower by the simultaneous and coordinated regulation of blower inlet pressure and blower speed.

Another object of the invention is to provide an improved manifold pressure control for an engine having main and auxiliary stage superchargers in which the auxiliary stage supercharger is governed by means responsive to a signal that is not amplied or otherwise aiected by the main-stage supercharger.

Another object is to provide an improved engine control device, adapted to be actuated either by the engine manifold pressure or by the pressure drop across the engine throttle, for regulating the speed of an engine driven supercharger.

Another object is to provide a method and apparatus for varying the speed of an aircraft engine supercharger impeller in accordance with Q changes in the pressure drop across a flow restriction located in either the inlet or the outlet passage of the impeller.

Another object is to provide means for maintaining a pressure drop across the throttle of an internal combustion engine which pressure drop is predetermined, and may be held constant, at varying engine manifold pressures.

Another object of the invention is to provide a control for an engine supercharger drive in which the pressure drop across the engine throttle is used to control the ow of fluid to fluid couplings in the supercharger drive.

Another object is to provide a proportional position control means for regulating the pressure drop across an engine throttle by controlling the oil ilow to an engine supercharger drive coupling, in which the change in position of the oil iiow control element is proportional to lthe deviation of the regulated pressure from the selected value.

Another object is to provide a proportional speed control means for regulating the pressure drop across an engine throttle by controlling the oil Bow to an engine supercharger drive coupling, in which the time rate of change of position of the oil ow control element is proportional to the deviation of the regulated pressure from the selected value.

Another object is to provide a combined proportional speed and proportional position control means adapted to regulate either the pressure drop across an engine throttle or the engine manifold pressure by controlling the oil ow to an engine supercharger drive coupling, in which the instantaneous change in position of the oil ilow control element is proportional to the deviation of the regulated pressure from the selected value and in which the time rate of change of position of the oil ow control element is proportional to the deviation of the regulated pressure from the selected value.

A further object is to provide improvements in the structure and operation of uid pressure responsive ow control devices.

Other objects and advantages will be apparent from the specification and claims, and from the accompanying drawings which illustrate what are now considered to be certain preferred embodiments of the invention.

In the drawings, Fig. 1 is a diagrammatic view, partly in section, of a supercharger control system constructed in accordance with the teaching of the invention.

Fig. 2 is an enlarged detail view, with part of the casing broken away, of the boost control shown in Fig. 1.

Fig. 3 is a chart illustrating the response of the control system of Fig. 1.

Fig. 4 shows a modied form of the regulator mechanism of Fig. l.

Figs. 5 and 6 are schematic enlarged Views of vmodified forms of a pilot valve for the regulator lita in Fig. 4.

Fig. 7 is a chart illustrating the response of a control system likethat shown in Fig. l when provided with the regulator of Fig. 4.

Fig. 8 is a diagrammatic View, partly in section, showing the regulator of Fig. 4 as used in a ccntrol system for a two-stage engine supercharger installation.

Fig. 9 is an enlarged sectional View of a modified regulator suitable for use with either singlestage or multi-stage engines, providing the performance of the regulator of Fig. 4 without the luse of inter-connecting linkages and eliminating one of the pilot valvesof the Fig. 4 system.`

Fig. l is a partial sectional view showing how the regulator of Fig. 9 may be actuated by variations in engine manifold pressure relative to a selected reference pressure.

Figs. ll and l2 are sectional details showing two modifications of the regulator of Fig. 9 for improving the response of the control during periods of acceleration or deceleration and when rst reducing altitude below critical.

Fig. 13 is a sectional view of a different form of the regulator shown in Fig. 9.

Fig. 14 is an enlarged detail view of a portion of the Fig. 13 structure.

Fig. l is a view showing schematically how the proportional speed regulator fica in Fig. 4. may be used alone to regulate throttle pressure drop.

Fig. 16 is a view showing schematically how the regulators 5e, @Qc shown in Fig. 4 may be used,

in combination, for directly controlling engine manifold pressure rather than throttle pressure drop.

One of the conventional types of control for regulating the manifoldY pressure of an engine having a supercharger driven at a variable .speed by fluid couplings is the sequential control in 'f which the throttle is opened fully before the fluid couplings are brought in, or engaged. In such sequential systems the damping required to stabilize the control of the couplings hinders the response in transferring to part-throttle operation because the throttle cannot beginto close until minimum supercharging is obtained. Further, when operating in the variable supercharger spe-ed range (full-throttle)- the response of the couplings is inherently slow, and small variations in manifold pressure cannot be corrected by the supercharger speed control.

The present invention, in what is now considered its most important aspect, includes a control means which may be used to obviate the above enumerated and other defects of the sequential type of system by enabling throttle positions and supercharger speed to be simultaneously, rather than sequentially, regulated, in a coordinated manner. The throttle may be maintained in working (or partially closed.) position at all times when the aircraft is below critical altitude for high blower, enabling small changes in manifold pressure to be corrected by the boost control, making the throttle always ready to reif'.

spend instanthT to a change in demand, and elimmating any liinderance to quick response by supercharger control damping.

From another aspect, the invention includes a control means which may be used for improving the operation, and. particularly the stability, of the sequential type, as well as of other types, of control system.

Referring to the embodiment of the invention illustrated in Fig. l of the drawings, I5 indicates generally a carburetor having a venturi li and throttle valves i2 in an induction passage lll leading to the individual cylinder intake pipes I5 of an internal combustion engine (partially shown at il), for example an engine of the type disclosed in Eobbs-Willgoos application, Serial No. 552,372, nled September l, 1944. A main stage super-charger impeller i8 in the induction passage I downstream from the throttle is mounted on a drive shaft 2) which is driven from the engine by a variable slip fluid coupling, indicated generally at 22. The driving element 28 of the coupling is connected to' an engine driven gear 24 on the lay shaft 25. The driven coubling element, or runner, 30 is connected to a gear 32 which meshes with a gear 34 on the supercharger drive shaft 2G. Thus, speed of the impeller I8 relative to engine speed is determined by the slip of the coupling, which depends upon the amount of oil supplied to the coupling.

Engine manifold pressure, or the pressure of theintake air in collector ring I5 and intake pipes i6, is controlled by a boost control mechanism generally indicated at 3S which is responsive to manifold pressure and which includes a manually operable lever 3S by which the pilot selects the value of manifold pressure desired. Supercharger impeller speed is separately, and simultaneously, controlled by a regulator generally indicated at ii which is responsive to carburetor loss, i.. e. the. pressure drop across the throttle valves i2', and which controls an oil metering valve 42 that meters the iiow of oil to the coupling 22.

Boost control. includes an expansible bellows 48 (-Fig.. 2) which communicates with the engine manifold l5, i6 by means of a conduit SEI, and a bellows 52 connected with bellows 48 by a link 55, the bellows 52 being evacuated and containing a spring 56 constantly urging the bellows 52 into Ianexpanded position. A- manually operable pilots lever 38, pivoted at 39 on a stationary fulorum, has a cam surface 31 bearing against one end 35 of a lever 58 which is fulcrumed at Ell on the connecting link 54 and is connected through the pin and slot 33 to a pilot valve 59 which controls the now of oil under pressure from conduit t5 to opposite sides of servo-piston 51 and the drain therefrom. A link 55 connects the servo-piston rod with one end of a lever 53 pivoted at 5| on a projection of the p-ilots lever. Another link 3i connects the upper end of lever 53 with the upper end of an arm 6l fulcrumed on a stationary pivot 4I. This arm is connected with and. actuates throttle valves l2 through link 62. The arrangement is such that, for any given setting of the pilots lever, an increase in manifold pressure above the selected value causes the pilot valve 39 to move down, porting oil to the left side of piston 5l' and moving it to the right so as to cause the throttle valves to close until the manifold pressure drops to the selected value. The action is similar, but opposite, upon a decrease in pressurebelow the selected value. Adjustment of lever 32 changes the selected value.

Regulator includes a bellows 64 which is vented through a conduit 66 to upstream cai'- buretor flange pressure and a bellows 58 axially aligned with bellows S4 which is vented through a conduit 'It to downstream carburetor flange pressure. A centerplate 'i2 forms ya wall between bellows 6l! and bellows 68, so that the centerplate is responsive to the pressure diiference between conduit 86 and conduit 1Q, or the pressure drop across the carburetor., referred to hereinv as carburetor loss. This pressure diderence is substantially the same as that directly across the throttle valves I2 and is used merely as a convenient source for measuring the pressure drop across the throttle. 1f desired, conduits 66 and 10 may be connected directly across the throttle, rather than across the entirer carburetor Il] as shown.

Centerplate T2. is operatively connected by means of an arm 'M with a pilot valve 76. This valve comprises two axially spaced lands, which in the intermediate, or null, position of the valve, block off passages i8 and 80 leading to opposite sides of a servo-piston 82 having a piston. rod 83 connected by an. intermediate link 84' to a connecting lever 86 pivoted at 88 on an extension of the regulator housing 90. The valve is supplied with oil under pressure entering into the space between its lands through a conduit 92, and is drained through a conduit 94. Centerplate 12 is constantly urged in a direction to contract bellows 64 by a tension spring 96 which is connected to the plate axially of the bellows at one end and is connected at its other end to a plunger 98 slidable in a wall of casing 96 and connected by a pin and slot connection H with the connecting lever 86 intermediate the ends of the latter. The connecting lever also has an intermediate pin and slot connection |02 with a valve rod |84 of the metering valve 42.

It will be evident that when carburetor loss balances the force setting of spring 96 the regulator is static. If the pilot selects a higher manifold pressure, by moving pilots lever 38 in the direction of the arrow, the throttle valves I2 will be opened by the boost control to correspond to the new position of the lever 3S, and, as a result, the pressure in manifold I6 will immediately increase to the selected higher value. However, opening of the throttle also increases the down stream carburetor ange pressure in the conduit F8 and bellows 68, causing plate 'i2 and pilot valve I6 to move to the left in Fig. 1, porting pressure oil from source 92 to the lefthand end of servo-piston 82 and moving it to the right. This movement of piston 82 to the right results in the movement of metering valve 42 to the right and opens port 43 leading into conduit 46, thereby increasing the liow from constant pressure source 44 to iiuid coupling 22. The working chamber of the coupling is continuously drained, in a known manner, through a restricted bleed or drain port 23. Thus the quantity of oil in the coupling working chamber, or the iilling of the coupling, changes with variations in the rate of flow of oil to the coupling through the conduit 46. When this rate of flow is increased by an opening movement of the metering Valve the resultant increase in the quantity of oil in the coupling working chamber decreases coupling slip so that supercharger I8 speeds up and tends to increase the rate of flow of air to the engine and to increase the manifold pressure in the intake pipes I3.

The action of boost control mechanism 36, however, is such as to prevent any change in manifold pressure, either above or below the selected pressure determined by the position of handle 38. Any increase in the manifold pressure within collector ring I5 and pipes i6 is communicated through conduit 59 to bellows 48 and moves the throttle valves l2 in a closing direction, until the manifold pressure returns to the selected value. Consequently, as the supercharger is speeded up in response to a decrease in the pressure differential across the throttle the resultant increase in manifold pressure due to increased supercharger speed acts on the boost control 36 through conduit and causes the throttle valves to move toward closed position, tending to restore carburetor loss towards its original value. The carburetor loss is not quite restored to the original value because of the follow-up action afforded by connecting lever 86 between metering valve 42 and spring 96. This will be evident when it is noted that the tension of spring et, or the force exerted by the spring on wall 12, is reduced as the metering valve l2 moves to the right and opens port 43, thus requiring less carburetor loss to bring the pilot valve 82 to the null, or balance. position. M

The chart shown in Fig. 3 graphically illustrates the response of this control system, as shown in Figs. 1 and 2, to asuddenly imposed change in manifold pressure selected by the pilot. As shown on the chart, a manual shift in the setting of lever 38 in a manifold pressure increasing direction is indicated by the change from L1 to L2 on graph I. This manual operation immediately causes the throttle to open, from position T1 to position T2 in graph II. As a result the manifold pressure instantly increases from P1 to P2 as shown in graph III. Opening of the throttle also causes an immediate decrease in carburetor loss from C1 to C2 in graph IV, thereby causing the metering valve 42 to open as shown by the change from V1 to V2 in graph V. Though the oil flow to coupling 22 immediately increases to a relatively high value, some time is required to iill the coupling and to increase the supercharger speed, which time interval is indicated schematically by the relatively fiat tops on the graphs at T2. V2 and C2. As the supercharger speed increases it tends to increase the manifold pressure. However, because of the large inertia of the rotating impeller, this action is slow relative to the operation of the throttle so that the boost control is able to maintain a substantially constant manifold pressure P2 by closing the throttle (as indicated at Ta) as the supercharger speed is increased. 'But the closing of the throttle tends to restore carburetor loss to its original value (see the rise C3 in graph IV) thereby causing the metering valve to close as shown by the drop V3 in graph V. The system nally becomes stabilized at a higher supercharger speed and, therefore, a new metering valve position, as shown at V4, of increased opening. Because the metering valve assumes a more open position (V4) in which the tension of spring 96 is decreased, the carburetor loss at the new mainfold pressure setting will be less as is shown by the offset X between the lines C1 and C4 in graph IV; the throttle will also be opened wider as shown by the difference between T1 and T4 in graph II. Therefore, in an installation which operates as shown in Fig. 3, the increase from P1 to P2 in manifold pressure is initially derived entirely from the opening of the throttle, but it is nally derived mainly from an increase in supercharger speed and only to a small extent from a more open throttle position.

The operation of this system (as shown in Figs. 1, 2 and 3) provides what may be termed proportional-position action, in that the position of the oil metering valve 42 is a linear function of the carburetor loss, the sense being increased oilrlow through the Valve 42 in response to decreased carburetor loss. The proportionality (merely a method of limiting vthe gain of the control) is the means used to obtain stability in the control system. A disadvantage of this particular system is that at minimum supercharger speeds an ap, preciable loss is taken across the throttles, resulting in ineicient use of the supercharger under some operating conditions.

In Fig. 4, a modied regulator mechanism has been shown which may be used with the control system of Fig. 1 and provides stability in the system and for relatively efcient use of the supercharger under all operating conditions. This modification includes a primary regulator unit 49' which is the same as the proportional position regulator of Fig. 1, except that. the connecting lever or follow-up lever 86a.. instead of being, directly ,Cenncted tethered@ wd i4-.a

unit. For a throttle closing and servo-motor piston 82 is extended and pivotally connected at its lower end through linlr` 8l to the mid-point |95 of a lever |08. Lever |08 is pivotallyconnected at its upper end' at pivot point i I with valve rod Illa and piston rod 83 of proportional-position piston 82 which rods, in this modication, are axially aligned. At its lower end, lever |88 is pivotally connected with a. rod I |-2` of' a reset piston I4 in an auxiliary regulator unit 40a. The reset piston is controlled by a pilot valve IIb` which ports oil admitted through conduit II from a substantially constant pressure source (not shown) to one or the other side of piston llt.. Oil is drained from the opposite sides of the valve through a conduit A now restriction, such as shown at |38, is provided in either or both of the pilot valve ports. Valve I I is4 operably connected by an arm |22 with a centerplate |24. between a pair of aligned bellows |26 and |28 subjected respectively to downstream and upstream carburetor pressure by conduits ISB and |32, which are connected respectively'to conduits 'It and 5%. Bellows |255 contains a compression spring 534, the force of which is adjustable by a screw 36. It will be noted that the regulator unit 46a, except for the provision of restriction |38, is generally similar in construction to the regulator 40 as shown in Fig. 1.

In operation, the action of regulator unit d of Fig. 4 is similar to that shown in Fig. 1. Piston t2 and valve rod I4a actuate the coupling metering valve as before, and the motion of the valve rod is transferred to follow-up lever 86a by lever |68'. During a transient, such as a change in selected manifold' pressure (a change in the setting of pilots lever 38), piston Il@ and pivot point |99 are essentially static (held substantially stationary) because of the restriction |38 in the oil passage leading to the left-hand side of piston I`I4. This result can also be accomplished by suitable variation in the configuration of the valve IIS. In either case the initial response of the system is a displacement of valve rod Iia (and consequently of metering valve 42) by regulator unit 48' proportional to the change in carburetor loss as in the system of Fig. 1.

The action of regulator unit 49', considered alone, is such that stabilization after a transient is achieved' only with an offset such as is indicated at X in Fig. 3. In the case of a throttle closing transient, the offset is an increase in carburetor loss; in a throttle opening transient, the oiiset is a decrease in carburetor loss. But the pilot valve lI I6 ci regulator unit 4ta is held in the null, or balance, position only when the carburetor loss balances the force of spring |34. Consequently the oifset resulting from an action of unit 40', whether it be in the increased or the decreased direction, is sensed by' the reset unit 4ta, and centerplate |24 moves or holds pilot valve Il away from the null position whenever carburetor loss is at a value diierent from that selected by the setting of spring |34 in the reset regulator transient, valve IIE is moved to the left in Fig. 4 porting oil to the left side of piston |I4. The resultant motion of piston |`|4 to the right is transferred through levers |138 and 86a, and reduces the loading of spring 96 in the regulator unit 4t', which results in action of piston 82 to move rod I4a to the left to reduce oiliiow through conduit 46 (see Fig. 1) to the coupling and hence reduce supercharging. Also Vcarburetor loss is reduced. For a throttle openingtransientl the actionsare reversed. Piston- ||4 becomesl static only' when the carburetor loss satisnes the setting of spring |34, so that regulator unit 40" is always brought back tol the desired setting by the4 reset unit 40a. The pilot valve ila'.` is preferably so designed and constructed thatthe rate-of-change of the position of reset piston H4 is roughly proportional to the deviation in carburetor loss from the value selected by spring |34, i. e. the change in position of piston I I4 is approximately the integral of the deviation. For instance, the valve IIS may be constructed as shown at IIB and IIS" in Figs. 5 and 6, in which the respective valve lands are provided with cylindrical and conical extensions H5, |I'I forming restricted passages H9, I2I that vary the now restriction of the inlet passages to piston III: in accordance with the displacement of the pilot valve. The action of reset regulator 49a may be made sufficiently slow' in this manner that no instability results'. If the pilot valve is formed either as shown at IIB in Fig. 5 or at H6 in Fig. 6 the restriction |38 may be either omitted or retained, as desired. The operation of this system (Fig. 4) provides what can be termed proportional plus floating control.

The response of a control system like that of Fig. 1, but utilizing the regulator modication of Fig. 4, is graphically illustrated in Fig. 7. As shown by this chart, the operation of the throttle and metering valve and the change in manifold pressure and carburetor loss in initially about the same as in the chart of Fig. 3. However,v in Fig. 7 the nal response is diierent in that the offset "'X is sensed by the regulator unit 4a, which after a time delay determined by restriction i3d [and/or restrictions H9 (Fig. 5) or restrictions iZI (Fig. 6)] operates to adjust the position of lever a and the tension of spring in regulator unit 4S until carburetor loss is returned to its original value. In installations utilizing either the restriction ||9 of Fig. 5 or the restrictions |2I of Fig. 6 the final adjustment may be made by a movement of the reset piston Ill at a speed determined by the amount of the offset, providing a gradual nal response as shown at V5, T5 and Cs in Fig. '7

In Fig. 8 the controls of Fig. 4 are applied to a two-stage supercharged engine including the main stage supercharger |811 discharging into the collector ring Iia and the engine induction pipes ia and which may be driven by the engine through a gear train and/or fluid couplings (not shown) connecting the engine crankshaft with the gear 34a onV the drive shaft 20a of the supercharger. Air is supplied to the supercharger Ia through thev intercooler I4@ and the carburetor Ilia (including a throttle |2a) in the induction passage I4a by an auxiliary stage supercharger |42 driven by the engine through a gear train (not shown) which connects the drive gears |43, |45 for the low speed ratio and high speed ratio couplings |44 and |46 with a drive shaft I9 that is connected to the engine crankshaft. Boost control 36a (which is the same as the control 36 in Fig. l) is vented tc manifold pressure in collector I5@ through conduit Ella. The oil rnetering valve 42a controls the ow of coupling working fluid from a substantially constant pre.,- sure source 44a through the conduit |50 t0 the low speed ratio coupling |44 and through conduit |52 to the high speed ratio coupling |45. It will be evident that as valve 42a moves to the right in Fig. 8 pressure oil is first metered to the low ratio fluid coupling |44 through conduit |58 and then (after the inlet port to conduit |50 is fully opened) is metered to the high ratio fiuidcou'- decimo pling through conduit |52. The bellows of regulator units 48 and 40a are connected to the upstream and downstream carburetor pressures as inFig. 4.

In the operation of the modiiication shown in Fig. 8, air from the free airstream enters the auxiliary stage supercharger |42 in which it is compressed and delivered to collector ring |48 from which it is delivered through intercooler |40 and carburetor lea to the main stage supercharger |8a. After compression by supercharger |8a, the air delivered by Way of collector ring |a and intake pipes |6a to the engine cylinders. The carburetor throttle valves |2a are operated by boost control 36a so as to regulate manifold pressure in the intake pipes |6c (in the manner described more fully in connection with Fig. l) to the value selected by manually operable pilots lever 38a. Valve 42a is actuated through valve rod |4a 46a, these units being vented to upstream and downstream carburetor flange pressures by conduits 66 and 16 respectively. The carburetor loss, or the value of the pressure loss maintained across the throttle valves, is determined (in the manner described in connection with Fig. 4) by the adjustment screw |36 for the spring |34 in the reset unit 46a. When the carburetor loss remains greater than this setting the metering valve 42a is closed and supercharger |42 idles. If the carburetor loss becomes less than the value selected by adjustment of spring |34, i. e. as the supercharger |42 demand increases, oil is metered rst to low ratio iiuid coupling |44 and then to high ratio coupling |46 until the auxiliary impeller speed is increased to a point suiiicient to bring the pressure drop across the carburetor back to the selected value. Whenever the high ratio coupling |46 carries the supercharger load, ring valve |54 within the low ratio coupling |44 shuts off the ow of oil into this coupling so that coupling |44 does not constitute a drag under these conditions. For a more complete description of the operation of the fluid couplings and the ring valve |54 reference is made to Hobbs- Willgoos Patent N o. 2,400,307, issued May 14, 1946.

In the arrangement of Fig. 8, since the throttling occurs downstream from supercharger |42, the power loss is negligible if the carburetor loss is held fairly low, for example two to three inches of mercury for some installations.

The modication shown in Fig. 9 accomplishes the performance of the control system shown in Fig. 4 Without interconnecting linkages and with a single pilot valve. In this construction a pilot valve |56 is slidable within a metering valve |58. Metering valve |58 is slidable within a cylindrical liner |66 which in turn is slidable within a stationary housing |62. It will be noted that pilot valve |56, metering valve |58, liner |66 and housing |62 are all concentric. Housing |62 and liner |60 form a chamber |64 which is connected through a restriction, or bleed, |66 to a drain conduit |68 which discharges into a sump (not shown). This sump is located above the level of the control so that conduit |68 is maintained full of oil. Chamber |16 formed between metering valve |58 and liner |66 is connected by a passage |12 to port |14 which is alternately connected either to a source |86 of oil under substantially constant pressure through annular spaces |16, |18, |86 and passages |82, |84 or to drain in chamber |88, depending on the disposition of pilot valve land |90 with respect to port |14. Chamber |92 between the pilot valve and the by the regulator units 48 and metering valve is connected by an axial passage |94 through the pilot valve to drain chamber |88. Pilot valve |56 is operated by a rod |96 connected to a diaphragm stern |96 to which are iixed two balancing diaphragme 266 and 262 and the carburetor loss diaphragm 264. Chamber 266 on the left side of diaphragm 264 is vented to the upstream carburetor Iiange pressure by conduit 268 (which may be connected to conduit 66 in Figs. 1 and 8) and chamber 2| on the right side of the diaphragm is vented to downstream carburetor iiange pressure (conduit 16 in Figs. 1 and 8) by conduit 2 i2. Diaphragm 264 and stem i 98 are urged to the left in Fig. 9 by a spring 2|4 acting against a wall 2|6 in the diaphragm housing; valve |58 is urged to the right by relatively stiff spring 2|8 acting against the opposite side of the housing wall 2|6 and valve liner |60 is urged to the left by a relatively soft spring 226 acting against the right hand end Wall of the housing |62.

Springs 2|8 and 226 tend to hold metering valve |58 against a stop 222 in liner |66. The valve and liner are so designed that in such a position (with valve |58 in abutment with stop 222) ports 224 and 226 leading respectively to the annular chambers 225, 221 are both closed by the left-hand land on the metering valve. As valve |68 moves to the left in Fig. 9, relative to the valve liner |66, port 224 is rst opened, metering oil from source |86 by way of chamber I 18 into chamber 226 and passage 228; then port 226 is opened metering oil from the passage |18 into chamber 221 and passage 230.

The pressure of oil in passage 228 acts with spring 232 to move piston valve 234 to the right to open port 236 leading to the low ratio hydraulic coupling |44 through passage 246 (which may be connected to conduit |59 in Fig. 8). This motion of valve 234 is resisted by the main oil pressure in source |86, to which the valve piston is subjected by a passage 23B, so that a constant pressure diierence is provided across port 224. Pressure of the oil in passage 236 acts with spring 242 to move piston valve 244 to the right to open port 246 leading to the high ratio hydraulic coupling |46 through passage 250 (which may be connected to conduit |52 in Fig. 8). motion is resisted by main oil pressure in chamdrgp across port 226.

The above described elements of the construction shown in Fig. 9 cooperate to provide what may be termed proportional-position plus nroportional-speed control, in the following manner. |56 is hydraulically balanced by fluid communication through passage |94 so spring 2|4. Thus and consequently the position of pilot valve |56 will bear a linear relationship to the carburetor loss, valve |56 moving to the right in Fig. 9 as the carburetor loss increases. Port |14 cooperates with land |96 so that metering valve |58 follows the pilot valve 56 as the latter moves; i. e. as pilot valve |56 moves to the right, port |14 is chamber |10 and enabling spring 2| 8 to move valve |58 to the right until land |96 again registers with or closes port |14. If the pilot valve |56 is moved to the left in Fig. 9 land |90 opens port |14 to main oil pressure in passage |86 by the position of diaphragm 264 way of port IZ and this pressure acting in chamber Ilo against valve |58 moves the latter to the left against the force of spring 2 I3 until port |14 again registers with or is closed by land |95. The configuration of port I'I'i and land i913 is preferably such that the action of the metering valve |58 in following the movements of the pilot valve |56 is nearly instantaneous; that is, a change in position of the metering valve |58 is eiected by a change in carburetor loss with minimum lag. It will be apparent that by virtue of spring 2|3, the pressure in chamber I'I relative to the pressure in drain conduit |58 bears a linear relationship to the position of valve |53. As the metering valve position is maintained in linear relation to the carburetor loss, the pressure in chamber I'Iil will vary linearly with carburetor loss but in the opposite sense; i. e. as the carburetor loss increases, pressure in chamber decreases.

Liner is urged to the right in Fig. 9 by pressure in cham er l'iil and is urged to the left by spring 22B. Spring 22|] preferably has a low rate, so that in eiect it is a constant eitort spring and could by modification of the design be replaced by a constant effort hydraulic piston. The load provided by spring 23SV is (by proper selection of the spring) made to balance the pressure achieved in chamber I'iil when the carburetor loss equals the desired value, i. e. when the desired Value of carburetor loss is obtained (and then only) spring 225 balances the pressure in chamber Ifi, and the liner Ifl is static. Whenever the pressure in chamber l'il does not balance the force ci ingY above or below the selected value) then liner |56 is moved relative to metering valve |53 so as to vary the oil now to the couplings through ports 221i, 22B until the carburetor loss, and consequently the pressure in chamber le'i, is rcturned to the selected value. However, this action of liner. |65 is delayed' in time, relative to movements of the metering valve, by the effect of iiow restriction |55. Thus, the compensating or readjusting movements of liner Iil occur only at a relatively slow rate, following a movement of the metering valve, or following a transient.

If the carburetor loss should increase above the selectedvalue metering valve |58 is moved to the right in Fig. 9 relative to liner |59 tending to close ports 225 and 22d (or either of them) in that order and reducing the oil flow to the couplings, thereby reducing the supercha-rging and the carburetor loss. A reverse. action results when carburetor loss fallsA below the selected value. This action, which is similar to vtheaction of the regulator unit Ml in Fig. 4 is proportional in that the change in metering valve position is proportional to the change in carburetor loss. Assuming that liner were nxed, this would result in a different carburetor loss for each metering valve position, as in the system of Fig. 1 and as shown byoffset X in Fig. 3. However, the increased carburetor loss above the selected value produces pressure in chamber Ifi. less than that obtained at the desired setting. The force of spring 225 being then greater than the pressure in chamber I'i, it urges liner ld to the leit, which closes ports 22d and 22s, (or either of them), thereby reducing the carburetor loss until the desired value is achieved; This action of liner |59 is delayed by the restriction I 56 (since oil must enter or leave chamber |64 through the restriction whenever liner Itis-moves springl 22d (carburetor loss be- 12 relative to housing |52), so that the liner acts in a manner similar to the regulator unit Gila in Fig. e1.Y to gradually reset the regulator foliowing a transient.

When a transient is imposed on the engine resulting in a decrease in carburetor loss below, the selected value metering valve |58 is moved to the left so as to increase the oil now to the couplings and the pressure in chamber Il() is increased above the equilibrium value overpowering spring 225 and tending to move liner |69 to the right, thus further opening the ports which regulate the flow of oil to the couplings. However, the motion of liner |58 is restricted, or damped, by the hydraulic restriction |55 since chamber |612 is lled with cil and as liner |50 moves this oil must now in or out through the restriction |56. The pressure drop across re striction |66 is proportional to the error in carburetor loss (the pressure in chamber |54 is always less than the pressure in chamber I'iD by a fixed amount, determined by the force of spring 22|), necessary to establish equilibrium of forces acting on liner |53). Therefore, if the restriction |56 is designed (for instance as a longv passage of small cross-sectional area) so as to have essentially capillary characteristics (flow rate proportional to pressure drop) the time rate of motion of liner |60 and of the resultant opening or closing of the coupling oil flow reguiating ports 226i, 226 may be made proportional to the error oi the controlled variable. This characteristic is generally termed proportionalspeed response.

The amount of opening of ports 221i, 226 in Fig. 9 and therefore the rate of flow of oil to the couplings is determined then by the proportional-position action of metering valve |53 and by the proportional-speed. action of metering liner H3G. As in the case or" Fig. 4, stability is provided by the position proportionality, and elimination of any offset is provided by proportional-speed action. The proportional-speed action is made sufciently slow by restriction |55 so as not to introduce instability into the4 control system. Performance of the Fig. 9 construction is essentially the same as that shown in the chart of Fig. 7. Obviously, this construction is equally applicable to single-stage engines (see Fig. 1) as to two-stage engines (see Fig. 6).

As shown in Fig. l0, the Fig. 9 construction may be used to control other variables than carburetor loss. For instance, it may be used to provide stable regulation of supercharger output to a constant manifold datum directly. This is accomplished by subjecting. diaphragm 26,4 to manifold pressure in conduit 5) and to a selected reference pressure in conduit 5i, respectively. Of course the throttle boost control 36 is then omitted.

To improve the response of the control during periods of acceleration, andwhen nrst reducing. the altitude below critical, it may be desired to by-pass bleed |56 in Fig. 9. One such arrangement is shown in Fig. 11. When the error (as indicated by the pressure drop acrossbleed |55) exceeds an arbitrary amount (which may be predetermined by proper selection o f spring 25| and spring 255), check valve 252 or check valve 254 will open automatically and allow unrestricted movement of liner IG until the error is reduced below this amount. Another automatically acting accelerator arrangement is shown in Fig. l2. When the error (as indicated by the position of pilot valve |56) exceedsl a:

13 predetermined amount, port 256 or port 258 is opened by movement of accelerator valve 251, allowing oil to I'low freely from chamber |64 through by-pass |61 to drain |68 and permitting unrestricted motion of liner |60 until the error is reduced below this amount.

Fig. 13 shows a modification of the Fig. 9 regulator. In the form shown in Fig. 13, the regulator comprises a housing composed of two sections 30| and 30|a in which piston 303 and a sleeve valve element 302, fixed thereto respectively reciprocate. Piston 303 cooperates with the housing 30| to form two chambers 304 and 305 on opposite sides of the piston. A valve member 306reciprocates within sleeve 302 and cooperates therewith to form variable flow regulating orices for the low speed coupling and the high speed coupling, respectively, by registry of ports 309, 3|0 in sleeve 302 with land 3|| of valve member 306. Member 306, which may be varied in length by adjusting means 340, is urged to the right by spring 312 and to the left by a spring 3|3 which is resiliently loaded by diaphragm assembly 3|4 through rod 3|5. The diaphragm assembly consists of a stem 301, an actuating diaphragm 3|6, a pair of balancing diaphragms 3|1, and associated connecting parts. Chambers 3|8, 3I9 formed between diaphragm 3|6 and cap pieces 320, 320 are connected respectively to upper carburetor ange pressure and lower flange pressure (for instance through conduits 66 and 10 in Fig. 1 or Fig. 8). Rod 3|5 contains annular grooves 32|, 322, 323, 324 forming lands 325, 326, 321, 328, 329. These lands t closely in bore 300 of an adapter 33| located between cap piece 320 and housing 30| and extending partially within the housing. Four of the lands, 325, 326, 321 and 328 have helical now restricting grooves cut on their periphery. Annular spaces 32| and 324 are connected by passages 332, 333 to chambers 304, 305 respectively. Passage 333 may be provided with a flow restriction, for instance (see Fig. 14) a helical restricted groove 334 formed between tapped hole 335 and a close tting screw 336 may be interposed between annulus 324 and chamber 305. The smooth surfaced land 329 controls the flow of .oil through ports 331, 338 to chambers 304, 305 respectively. The several chambers 34| are connected to drain by the passages |68. Oil under substantially constant pressure is supplied to the regulator by conduits |86. The pressure drops across the coupling oil flow regulating orifices 308, 3|0 are controlled by valves 234, 244 which are the same as in Fig. 9.

The regulator of Fig. 13 functions as follows. Oil is supplied under pressure by conduit |86 to annuli 322 and 323 from whence it flows through the helical grooves of lands 326 and 321 to annuli 32| and 324 and thence through the helices of lands 325 and 328 to drain 34|. The oil undergoes a gradual reduction in pressure as it ows through the restricted grooves. By reciprocating rod 3|5 in bore 300, the effective length of the grooves in lands 325 and 328 (the length of the passage in which oil is constrained to ow) may be varied. That is, as the rod is moved to the right, the ow path from annulus 32| to drain 34| is lengthened, and the ow path from annulus 324 to drain 34| is shortened, resulting in increased pressure at annulus 32| and decreased pressure at annulus 324. When the rod is moved to the left the converse obtains. The null position of rod 3|5 is dened as that position at which the pressures in annuli 32| and 324 are equal. The pressure diierence between annuli 32| and 324 (for the condition when there is no flow through passages 332 and 333) is very nearly a linear Iunction of the displacement of the rod from the null position, within the design range of operation.

Rod 3|5 is urged to the right by springs 3|2 and 3|3 and is urged to the left by the pressure difference (carburetor loss) between chambers 3|8, 3|8 acting on the net area of diaphragm 3|6. Since the area of piston 303 acted upon by the pressure in chamber 305 is equal (or substantially equal) to the area of the piston acted upon by the pressure in chamber 304, the regulator is static when rod 3|5 is in the null position because in this position the pressures in annuli 32|, 324 and consequently the pressures in chambers 304, 305 connected thereto by passages 332, 333, are equal. The pressure difference (carburetor loss) required across diaphragm 3|6 to balance the force of springs 3| 2, 3|3 when rod 3|5 is in its null position is dened as the setting of the regulator and may be varied by adjustment 340.

applied across piston 303 and will cause it (and the valve sleeve 302 connected thereto) to move, opening or closing orices 309, 3|0 successively as required to correct the deviation by varying the rate of oil flow to the couplings. The helicalgrooves in lands 325, 326, 321 and 328 preferably have capillary characteristics (i. e. ilow proportional to pressure drop), and when this is the case piston 303 will attain a velocity approximately proportional to the displacement of rod 3|5 from its null position. In some installations, if suiiicient throttling cannot otherwise be obtained by the helical grooves on the lands of rod 3|5, it is proposed to apply the pressure difference from annuli 32| 324 across the helical flow restriction 334 between the screw 336 and the threaded bore 335. In other installations the auxiliary helical restriction 334 may be omitted.

From the above description it is seen that the response of the Fig. 13 regulator to a deviation in carburetor loss may be described as proportional-position plus proportional-speed. Valve member` 306 is moved directly by diaphragm assembly 3|4 providing an instantaneous change in oil Ilow proportional to the deviation, thus providing a proportional position action. To correct the offset (see X in Figs. 3 and 7) which would otherwise be obtained upon reestablishment of equilibrium, the piston 303 is moved at a velocity proportional to the deviation by flow through passages 332, 333 created by the pressure difference between annuli 32|, 324 whenever rod 3|5 is away from its null position. Stability is provided by limiting the ratio of the travel of valve member 306 to the deviation, and by providing suiiciently low velocities of piston 303 and liner 302.

When the proportional-position variables are such that the full opening or closing of orificesl Whenever anydeviation from this setting is experienced, rod

309, 310 is not obtained with maximum attained deviations of carburetor loss, the response of the control to transients requiring a large change in coupling oilflow (for an acceleration from engine neutral cruise power to high blower military power for example) is limited by the viscous damping applied to piston 303. This condition is obviated by an accelerating means comprising the land 329 and ports 321, 328. If carburetor loss deviation exceeds a predetermined maximum rod 315 is shifted far enough to move land 329 away from either port 32 or port 328, depending on the direction in which the rod is shifted. The result is to port one or the other of chambers 304, 305 directly to inlet pressure, thus lay-passing the viscous damping whenever the deviation exceeds predetermined limits, so that the response to said transients will be immediate.

The Fig. 13 form of regulator provides an improved method of viscous damping, wherein the proportional speed action is obtained independently of the proportional-position response. It also provides an improved method of by-passing the viscous damping to improve response to transients involving large changes in control output, and it provides an improved mechanical construction, wherein large amounts of follow-up action (synonymous with small proportional piston response) can be obtained with lighter springs.

The various regulator combinations and constructions described above are adapted for use in controlling other variables than carburetor loss. For instance, the Fig. 13 construction might be used to regulate engine manifold pressure directly, by applying manifold pressure to one side of diaphragm 3|6 through conduit 283, the other side of the diaphragm being subjected to a selected variable reference pressure through conduit 210, as in the case of Fig. 10. The regulator will then be directly responsive to manifold pressure and will function to vary the oil flow to the couplings and control supercharger speed so as to maintain the manifold pressure, or supercharger outlet pressure, in predetermined relationship to the selected reference pressure..

Further, certain sub-combinations, or units, of

the regulator constructions previously described may be used per se for control purposes. Thus,

Fig. 15 shows schematically how the proportional speed regulator unit 40a of Figs. 4, 5 and 6 can be used alone for regulating the loss across the carburetor l0. In Fig. 15 engine manifold pressure is regulated by the boost control 3B as in the case of Fig. 1. However, carburetor loss is regulated by the proportional speed regulator unit 43a, rather than by the proportional position regulator of Fig. 1.

Fig. 16 shows schematically how the v,combined proportional-position and proportional-speed regulator of Figs. fl, 5 and G may be used to pro vide stable regulation of supercharger output to aconstant manifoldpressure datum directly. Instead for being connected across the carburetor, the regulator of Fig. 1G is connected directly to the outlet side of the supercharger and to a source providing a selected variable pressure, so that the regulator is subjected to a maniold'pressure signal and to a selected reference pressure in the same manner as in the modification of Fig. '10. In Fig. 16 the regulator units t9 and ma actuate the metering valve yt2 ,to control the flow .of oil to coupling 22 so as to regulate :the :speed of supercharger IS exactly Aas in the case of Fig. 4. But -in Fig. A16 the regulator 'bellows B4 and :28

are vented to manifold pressure through conduit 5f] (rather than to upstream carburetor iiange pressure), while the bellows 68 and 126 are vented through conduit 5l to a source 460 providing a selected reference pressure (rather than being vented to downstream carburetor flange pressure). Therefore the regulator will control supercharger output so as to maintain the engine manifold pressure in the intake pipes I5 at a constant value relative to the selected pressure in source 460,

The reference pressure source 430 comprises a manually operated pilots lever 3S' movable about a pivot 502 so as to change the position of a fulcrum A04 of a lever 563 interconnecting stem 498 on an evacuated bellows 410 and stem 412 of a balanced valve 4M. This valve when moved to the right from its null position admits fluid (such as oil) from a substantially constant pressure source dit through port 4i? into the pressure chamber 4 l S surrounding the bellows 4 I n. When moved to the left, valve 4M opens port 4H and chamber M8 to drain through conduit 420. Bellows ille is expanded by spring 422 therein and is contracted by the fluid pressure in chamber sie. These movements of the bellows are transmitted to valve is by lever 4&6 in such manner as to regulate the pressure in chamber M8 to a constant value selected manually by the position of pilots lever 33 and fulcrum 40.4. For any given setting of the pilots lever, an increase in pressure in chamber H8 above the selected value will collapse bellows M0 and move valve 414 to the left, opening port 4 l 'i to drain until the cham.-

-- ber pressure is returned to the selected value.

If the chamber pressure falls below the selected value bellows d l is expanded by spring 422 which shifts valve It to the right and ports the chamber to inlet pressure in conduit M6, until the chamber pressure is returned to the selected value.

The regulator units 46 and 40a in Fig. 16 function so as to maintain the engine manifold pressure at a substantially constant value relative to the reference pressure in bellows .68 and |25. As this reference pressure may be changed, or selected, by the pilots lever 3,8' it will be apparent that engine manifold pressure will, by the units Q3', 'tim and 4&0, be regulated to a constant datum that Vcan be selected by the pilots lever.

The engine throttle has not been shown in Fig. 16. if a throttle is provided in an installation such as shown in Fig. 16 (or Fig. 10) it is preferably operated either manually or automatically, in a known manner, in sequence with the supercharger regulator. In such an arrangement, the superoharger is inactive or idles during part throttle operation and the supereharger regulator operates Yto control manifold pressure only for operating conditions above full throttle.

Several embodiments of the invention have been shown and described herein, but it will be understood that the invention is not limited -to the details of construction, or of the specific combinations and arrangements of elements herein illustrated, `but covers al1 such forms as fall within the scope of the appended claims.

I claim:

i. In an engine having an induction system, a supercharger and a throttle in said induction system, means including a variable slip fluid coupling for driving said supercharger, and means responsive to the pressure on the upstream side of said throttle and the pressure between `[the 17 throttle and supercharger for controlling the speed of said supercharger by varying the slip of said iluid coupling.

2. In an engine having a supercharger, a variable slip fluid coupling for driving said supercharger at a variable speed relative to said engine, means for varying the speed ratio of said coupling with changes in the position of a control element, proportional-position means for relatively quickly changing the position of said control element by amounts proportional to deviations from a predetermined value of a fluid pressure that is affected by the speed of said supercharger, resetting means for relatively slowly adjusting said control element until said uid pressure is returned to said predetermined value, a throttle for regulating the engine intake air pressure, and in which said fluid pressure deviations are the variations from a predetermined value of the pressure on one side of said throttle relative to the pressure on the other side thereof.

3. Apparatus according to claim 2, including means associated with said resetting means for causing said control element to be adjusted by said resetting means at a speed proportional to deviations in said fluid pressure from the predetermined value.

4. In combination with a pair of compressors arranged in series in a fluid passage, a movable throttle in said uid passage for controlling the delivery pressure of the downstream compressor, and means for varying the speed of the upstream compressor to maintain a measured fluid pressure drop across said throttle, the speed of the upstream compressor, or auxiliary supercharger, is controlled in accordance with changes in the outlet pressure thereof relative to the inlet pressure of said downstream compressor, or main stage supercharger, by varying the slip of a fluid coupling.

5. Apparatus for regulating the oW of a fluid comprising, a metering element, means responsive to a fluid pressure for moving said element to positions determined by the deviation of said vpressure from a selected value, a metering member associated with said element and cooperating therewith to form at least one now restriction the capacity of which is varied at a relatively fast rate by movements of said element so as to control said regulated iluid flow, and means for operating said member at a relatively slow rate for further varying 4the ow capacity of said restriction by changing the relationship between said element and said member.

6. Apparatus according to claim 5 including means lfor operating said metering member at a speed which varies in accordance with the 'deviation of said pressure from the selected value and further including means for maintaining a substantially constant pressure drop across said flow restriction.

7. Apparatus according to claim 6 in ywhich the speed of operation of said metering member is determined Iby a fluid pressure that varies as a function of the position of said metering element and which acts on both said metering element and said metering member.

8. Apparatus according to claim 6 in which the speed of operation of said metering member is determined by a pressure difference created by said deviation.

9. Apparatus according to iclaim 6 including accelerator means automatically effective only when the deviation of said pressure from the selected value exceeds a predetermined maximum to render said metering member operative at a relatively fast rate so long as said deviation exceeds said maximum value.

10. Apparatus according to claim 5 in which the speed of operation of said metering member is determined by a fluid pressure that varies as a function of the position of said metering element and which acts on both said metering element and said metering member.

11. Apparatus according to claim 10 including accelerator means automatically eiective only when the deviation of said pressure -from the selected value exceeds a predetermined maximum to render said metering member operative at a relatively fast rate so long as said deviation exceeds said maximum value.

12. Apparatus according to claim 5 in which the speed of operation of said metering member is determined by a pressure difference created by said deviation.

13. Apparatus according to claim 12 including accelerator means automatically effective only when the deviation of said pressure from the selected value exceeds a predeterminedmaximum to render said metering member operative at a relatively fast rate so long as said deviation exceeds said maximum value. f

14. Apparatus according to claim 5 including n accelerator means automatically effective only when the deviation of said Ipressure from the selected value exceeds a predetermined -maximum to render said metering member operative at a relatively fast rate so long as said deviation exceeds said maximum value.

15. In an engine having an induction passage, a supercharger and a throttle in said passage,

means for varying the output of said supercharger in accordance with movements of a control element in response to variations in the pressure drop across said throttle, and means for moving said control element ata velocity proportional to the ldeviation of said pressure drop from a selected value.

16. Apparatus according to claim 15 including a boost control responsive to the engine combustion chamber intake pressure, or the delivery pressure downstream of the compressor, for automatically controlling said throttle.

17. In an engine having an induction system, a supercharger and a throttle in said induction system, means including a hydraulic coupling for driving said supercharger, and means responsive to the pressure drop across said throttle for controlling the speed of said supercharger through said hydraulic coupling including a housing, a pilot valve, a diaphragm operably connected to said pilot valve, a conduit for connecting one side of said diaphragm to said induction passage upstream of said throttle valve, another conduit for connecting the other side of said diaphragm to said induction passage downstream of said throttle valveJ a sleeve valve, said pilot valve slidably positioned in said sleeve valve to control the flow of a fluid to said hydraulic coupling.

18. In an engine having a main stage supercharger and an auxiliary stage supercharger Whose outlet is connected to the inlet of the main stage supercharger by a duid passage, a variable restricting device in said fluid passage, means responsive to the engine combustion chamber intake pressure for regulating said intake pressure by varying the restricting device, and means for varying the outlet pressure of said auxiliary stage supercharger in accordance with variations 19 in the pressure drop across said restricting device from a selected value.

19. Apparatus according to claim l, including a boost control responsive to the engine combustion chamber intake pressure, or the delivery pressure downstream of the compressor, for automatically controlling said throttle.

20. Apparatus according to claim 1, including a boost control responsive to the pressure downstream of the throttle for automatically controlling said throttle.

21. In an engine having a supercharger and a throttle, a variable slip fluid coupling for driving said supercharger at a variable speed relative to said engine, means for varying the speed ratio of said coupling with changes in the position of a control element, means for relatively quickly changing the position of said control element by amounts proportional to deviations from a predetermined value of pressure drop across the throttle, resetting means for relatively slowly adjusting said control element until said pressure drop is returned approximately to said predetermined value.

22. Apparatus according to claim 21 including a boost control responsive to a pressure downstream of said throttle for automatically controlling said throttle.

23. In an engine having an induction system and a combustion chamber, a throttle in said induction system, means responsive to the engine combustion chamber intake pressure for regulating said intake pressure by varying said throttle, a supercharger in said induction system between the throttle and combustion chamber intake, and means connected across said throttle Vfor varyingthe speed of said supercharger in accordance with variations in the pressure drop across said throttle from a selected value.

24. In an engine having an induction system and a combustion chamber, a main stage supercharger and an auxiliary stage supercharger in said induction system, a variable restricting device in said induction system, means responsive to the engine combustion chamber intake pressure for regulating said intake pressure by Varying the restricting device, and means connected across said restricting device for varying the speed of said auxiliary stage supercharger in accordance with variations in the pressure drop across said restricting device from a selected value.

RICHARD J. COAR.

References Cited in the :tile of this patent UNITED STATES PATENTS Number Name Date 991,641 Plantinga May 9, 1911 1,390,829 Smoot Sept. 13, 1921 2,240,515 Partington May 6, 1941 2,267,437 Alfaro Dec. 23, 1941 2,393,172 Larrecq Jan. 15, 1946 2,400,306 Hobbs May 14, 1946 2,400,830 Kinnucan et al. May 21, 1946 2,422,162 Borell June l0, 1947 2,491,482 Dolza et al Dec. 20, 1949 2,575,345 Jorgensen et al Nov. 20, 1951 FOREIGN PATENTS Number Country Date 205,291 Switzerland Sept. 1, 1939 125,004 Australia June 26, 1946 

